OF MUTANT CHARACTERS. 



131 



(table 3). These two crosses gave identical results as to the distribu- 

 tion of both characters and sex, which proved that no sex-linkage was 

 involved. They may therefore be combined and considered together. 



The total number of flies produced was 2,857, of which 772 or 27 per 

 cent were speck, which is in agreement with the fact that speck is a 

 simple autosomal recessive. 



TABLE 3. PI speck olive cf X wild 9 ; FI mid- 

 type 9+^1 wild-type cf. 



The inheritance of " olive" was also followed, but since this will be 

 treated in the following section it need only be stated here that the 

 ratio of wild-type to olive was 9 : 7, which indicates two recessive body- 

 color genes giving similar somatic effects and assorting independently 

 of one another. One of these is olive III, (Ill-chromosome recessive) 

 and the other, olive proper (II chromosome, closely linked to speck) . 



Speck olive males were crossed to black females, and 5 F 2 pah* cul- 

 tures (table 4) and 5 more from the reciprocal (table 5) were raised. 

 The significant fact observed in these crosses was that none of the 

 blacks were speck, which means that speck has its locus in the second 

 chromosome. The combined data (disregarding olive) give 1,098 

 wild-type, 490 black, 466 speck, black speck, which is an approxi- 

 mation to the 2:1:1:0 ratio expected from such a cross. 



TABLE 4. PI, speck olive cf X black 9; FI wild-type 9 -f FI wild-type d*. 



